Cellylar respiration

Forms of Energy

  • A diver has more potential energy on the platform than in the water.
  • Diving converts potential energy to kinetic energy.
  • Climbing up converts the kinetic energy of muscle movement to potential energy.
  • Notable Point: A diver has less potential energy in the water than on the platform.

The Laws of Thermodynamics

Key Principles

  1. Energy can be transferred or transformed, but neither created nor destroyed.
    • Example: The chemical (potential) energy in a fish will be converted by a bear into kinetic energy while running.
  2. Every energy transfer or transformation increases the disorder (entropy) of the universe.
    • As the bear runs, disorder is increased around it in the form of heat and the small molecules that are by-products of metabolism.

Free Energy Changes (ΔG) in Exergonic and Endergonic Reactions

Exergonic Reaction

  • Definition: Energy released, spontaneous reaction.
  • Diagram Explanation:
    • Reactants transform into products by releasing energy.
    • Free Energy Change (ΔG < 0): Indicates the reaction releases energy.

Endergonic Reaction

  • Definition: Energy required, nonspontaneous reaction.
  • Diagram Explanation:
    • Reactants require energy to transform into products.
    • Free Energy Change (ΔG > 0): Indicates the reaction requires energy.

The Structure of ATP

Adenosine Triphosphate (ATP)

  1. Structure Components:
    • Adenine
    • Ribose
    • Phosphate Groups
    • Chemical Structure:
      • Diagram of ATP showcasing its components (Adenine, Ribose, and Phosphate groups).

Hydrolysis of ATP

  • Process: ATP hydrolysis leads to the formation of Adenosine Diphosphate (ADP) and inorganic phosphate, releasing energy.

ATP and Work

Types of Work Powered by ATP

  1. Transport Work

    • Mechanism: ATP phosphorylates transport proteins.
    • Example: Membrane protein transports solutes.

  2. Mechanical Work

    • Mechanism: ATP phosphorylates motor proteins.
    • Example: Movement of proteins.

  3. Chemical Work

    • Mechanism: ATP phosphorylates key reactants.
    • Example: Conversion of reactants to products.

The ATP Cycle

  • ATP synthesis from ADP and inorganic phosphate requires energy.
  • ATP hydrolysis to ADP and inorganic phosphate yields energy.
  • Energy for cellular work involves endergonic processes, while energy from catabolism includes exergonic, energy-yielding processes.

Energy from Glycolysis

Glycolysis Overview

  1. Energy Investment Phase

    • Input: 1 Glucose molecule, 2 ADP, and 2 inorganic phosphates (P).
    • Outcome: 2 ATP used.

  2. Energy Payoff Phase

    • Output: Produces 4 ATP, and 2 NADH, leading to the net gain.
    • Final Products: 2 Pyruvate and 2 H₂O, alongside the net yield of 2 ATP after accounting for initial investment.

Fermentation Processes

Lactic Acid Fermentation

  • Inputs: 2 ADP and 2 P, converted from glucose.
  • Outputs: Produces 2 ATP and 2 Lactate from 2 Pyruvate.

Alcohol Fermentation

  • Inputs: Similar initial glucose breakdown as in lactic fermentation.
  • Outputs: Produces 2 Ethanol and 2 CO₂ from 2 Pyruvate following glycolysis.

Substrate-level Phosphorylation

  • Definition: A process where ATP is generated during glycolysis and the citric acid cycle directly through the transfer of a phosphate group to ADP, forming ATP.
  • Diagram Reference: Shows key enzymes involved in substrate-level phosphorylation, such as pyruvate kinase and phosphoenolpyruvate (PEP).

Citric Acid Cycle

  • Involves the conversion of Acetyl CoA into NADH, FADH2, and ATP; releasing CO₂.
  • Each glucose molecule results in 2 Pyruvate entering the cycle, yielding 2 CO₂ and generating ATP via substrate-level phosphorylation.

Electron Transport Chain

  • Location: Occurs in the inner mitochondrial membrane.
  • Role: Transfers electrons via NADH and FADH₂ through a series of multiprotein complexes, ultimately leading to the production of water.
  • Generates a proton-motive force, aiding in ATP synthesis.

Counting ATPs

  • NADH and FADH₂ generated through pathways yield ATP during oxidative phosphorylation.
  • Maximum ATP yield per glucose: Approximately 30-32 ATP.

CAC: The Metabolic Hub of the Cell

  • Function: Central role in metabolizing carbohydrates, fats, and proteins.
  • Serves as a key junction for various metabolic pathways, supporting cellular respiration and energy production.